How to calculate precision hit point shoot at Character

Hello everyone, i have some problem that want to ask pro unity 3d.

I want to calculate precision hit point in body character,example how to determine hit point at head's character, how to determine hit point at arm's character, at chest's character, at stomach's character, at leg's character, i were try add collider for separator child object of models, but have problem with Character Controller Component, So how to I fix that problems ! Please help me !